Fluid pressure operated devices for radially expanding portions of tubing are known, such devices being disclosed in U.S. Pat. Nos. 1,448,457; 2,479,702; 2,938,562; and 3,200,627. Structures of these patents include fluid conveying mandrels to hold the tubing, and die elements against which portions of the tubing are flared or otherwise formed by fluid pressure. These expanding devices are customarily used to provide short bulges in tubing for coupling purposes and the like. In addition, they are used to expand tubing to fit fins and other apparatus connected to the outer surface of the tubing.
Several hydraulic chucks have been developed which are suitable for tightly gripping one end of the elongated tube while simultaneously delivering a tube expanding fluid. Among these are U.S. Pat. Nos. 3,505,846; 3,813,751; 3,962,769; and 4,189,162.
One of the problems which continuously plague those users of hydraulic chucks is the inability to employ them after the exterior of the tube has been modified. All of the above described hydraulic chucks engage the outside of the tube as well as the inside, and for that reason cannot be used in systems where fins, plates and other components extend up to the edge of the tube. Many tube and shell arrangements for heat transfer, such as in nuclear energy facilities, are employed where the header plate is located at the end of the tube. Even though prior art hydraulic chucks cannot engage the tube, these shell and tube configerations need to be tested for fluidic soundness and safety.
Not only is it necessary to engage the interior of said tube, it is necessary to deliver fluid to the interior of said tube at sufficient pressure to test the tube at or above the pressure at which it is intended to operate. Accordingly any device which engages the interior of the tube should preferably prevent passage of fluid in unwanted areas, such as inadvertently out the end of the tube.
Yet another feature which would be of advantage in a hydraulic chuck adapted to engage the interior of a tube is the ability to grip the fluid independently of the amount, if any, of fluid pressure in the tube. This feature would permit preloading of the tube with the fluid to avoid surges and other disruptive effects. Nevertheless it would be additionally helpful if the grip on the tube, and the seal between the tube and the hydraulic chuck, could be increased in strength as the fluid pressure in the tube is increased.